In the manufacture of tablets, particularly for use in the pharmaceutical industry, an active drug is generally mixed with an excipient, that is an inert diluent, such as, for exaple, lactose, starch, or magnesium carbonate. The excipient not only dilutes the active drug but also improves the compressability of the drug helping to form a better tablet. Particularly in high speed tablet machines used in commercial production it has also been found necessary to add lubricants to the formulation such as, for example, magnesium stearate, calcium stearate and stearic acid. Absence of or insufficient lubricaton in a tablet formulation can lead to poor quality of the finished tablet, sticking of material onto the punch faces, and damage to the machine. However, the use of lubricants in the tablet formulation has a number of disadvantages. Most lubricants are hydrophobic and when present in a tablet tend to inhibit or slow down the disintegration and dissolution of the tablet. This in turn will affect the bio-availability of the active drug. Secondly the lubricant will often decrease the compressibility of the tablet formulation. This results in a softer tablet which is more friable. In addition, the lubricant will sometimes react chemically or physically with the active drug or excipients causing such problems as discoloration or a loss in activity of the active drug.
A method of spraying lubrication on the punches of a single station tabletting press is disclosed in U.S. Pat. No. 3,461,195. However, this method is not practical for use in commercial production on a rotary press. U.S. Pat. No. 3,042,531 discloses a method of applying lubricant to the dies and punch faces of a commercial tabletting press by first tabletting a lubricated material such as lubricated sodium chloride.